JP2002031817A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: In a liquid crystal display device, the amount of light incident from the back surface of an array substrate directly incident on a semiconductor layer forming a channel is reduced, and deterioration of off-characteristics of a TFT is suppressed. SOLUTION: On an insulating transparent substrate, a plurality of pixel electrodes 10, a source line 5, a gate line 2, and a semiconductor layer 4 formed in a one-to-one island shape on the pixel electrode are arranged in a matrix. In the liquid crystal display device in which the semiconductor layer 4 constitutes a thin film transistor, the semiconductor layer 4 is in a plane direction more than the gate wiring 2a except for an intersection with the source electrode 5a or the drain electrode 9 and its vicinity. Inside. Since the semiconductor layer 4 is hidden inside the gate line 2a when viewed from the back surface of the array substrate, backlight light does not enter the semiconductor layer 4 and light from the back surface on the array substrate side is smaller than that of the conventional liquid crystal display device. Is suppressed from increasing the carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device using thin film transistors.

[0002]

2. Description of the Related Art A display device to which liquid crystal is applied has low power and light weight, which are not features of a conventional display. The liquid crystal display device is used for a notebook computer, a car navigation display, and the like because a clear image display with less crosstalk can be obtained. In recent years, the liquid crystal display device has been rapidly used as a large display monitor.

Hereinafter, an example of a conventional active matrix type liquid crystal display device will be described with reference to the drawings. FIG. 3 is a partially enlarged plan view showing a part of an array substrate in a conventional active matrix type liquid crystal display device. In FIG. 3, 2 is a gate wiring and 4 is TF
An amorphous silicon semiconductor layer forming T channel, source and drain regions, 5 is a source signal line, 9
Is a drain electrode of the TFT, and 10 is a pixel electrode made of ITO or the like. A portion serving as a gate electrode 2a protrudes from the gate wire 2 below the semiconductor film 4 in a branch shape, and a portion serving as a source electrode 5a protrudes from the source wire 5 above the semiconductor film 4 in a branch shape. . The drain electrode 9 and the pixel electrode 10 are electrically connected via a contact hole 7 opened in the passivation film.

FIG. 4 is a cross-sectional view of the entire liquid crystal display device taken along the line BB 'in FIG. On an upper surface of a glass array substrate 1, a gate wiring 2, a gate insulating film layer 3, a semiconductor layer 4, a passivation film 6, and a pixel electrode 10 are sequentially laminated.

The operation of the liquid crystal display device configured as described above will be described. First, a voltage is applied to the gate electrode 2a, and the amorphous silicon semiconductor layer 4 of the TFT is formed.
When a channel is formed in the TFT, the video signal from the source electrode 5a passes through the channel of the TFT and passes through the drain electrode 9a.
And transmitted to the pixel electrode 10. Then, an electric field corresponding to the video signal is generated between the pixel electrode 10 and the counter electrode 11, and the orientation of the liquid crystal injected between the pixel electrode 10 and the counter electrode 11 changes according to the generated electric field. Thereby, the transmittance of the light incident from the back surface of the array substrate 1 changes, and an image corresponding to the video signal is displayed.

In the above-mentioned conventional liquid crystal display device, the semiconductor film 4 has a gate electrode 2a as shown in FIG.
Is formed wider than the gate electrode 2a so as to cover the edge portion of the gate electrode 2a. This is a configuration necessary in principle to form a gate region and a drain region of a TFT.
Further, it is also to prevent the gate electrode 2a from being electrically short-circuited with the source electrode 5a or the drain electrode 9 at the edge of the gate electrode 2a. Gate electrode 2a
In the edge portion, the coverage of the gate insulating film 3 is deteriorated. Therefore, when the source electrode 5a and the drain electrode 9 are formed directly on the edge portion, an electrical short-circuit easily occurs between the two.
Therefore, by covering the edge of the gate electrode 2a with the semiconductor film 4, the occurrence of such a short circuit failure is prevented.

[0007]

However, in the above-mentioned conventional liquid crystal display device, when light is irradiated from the back surface of the array substrate 1, a part of the incident light is applied to the semiconductor film 4 as shown in FIG. Directly incident. The light incident on the semiconductor layer 4 unnecessarily increases the carrier concentration of the semiconductor layer 4 and lowers the electrical resistivity, thereby deteriorating the off-characteristics of the TFT. When the off-characteristics of the TFT deteriorate, image performance such as contrast deteriorates. In recent years, with the demand for a display device having higher luminance, this kind of problem has become more serious.

The present invention has been made to solve the above-described problem, and reduces the amount of light incident from the back surface of the array substrate to be directly incident on a semiconductor layer forming a channel. It is an object of the present invention to provide a liquid crystal display device capable of suppressing a decrease in image performance.

[0009]

In order to achieve the above object, a liquid crystal display device according to the present invention comprises a plurality of pixel electrodes arranged in a matrix on an insulating transparent substrate, and a column of the pixel electrodes. A source wiring formed therebetween, a gate wiring formed between rows of the pixel electrodes, a semiconductor layer formed in a one-to-one manner on the pixel electrode, and connecting the semiconductor layer and the pixel electrode. A liquid crystal display device having a connection electrode, wherein the semiconductor layer constitutes a thin film transistor using a part of the source wiring as a source electrode, a part of the gate wiring as a gate electrode, and the connection electrode as a drain electrode. The semiconductor layer is located inside the gate wiring in the plane direction except for the intersection with the source wiring or the connection electrode and the vicinity thereof.

As a result, except for the intersection with the source or drain electrode and its vicinity, the semiconductor layer is hidden inside the gate wiring. Compared with the display device, an increase in carriers due to light from the back surface on the array substrate side is suppressed. Therefore, it is possible to suppress a decrease in image performance caused by TFT characteristic deterioration. In the vicinity of the intersection, the semiconductor layer is located outside the gate wiring, and the edge of the gate wiring is covered with the semiconductor layer. Therefore, occurrence of a short circuit between the gate wiring and the source or drain electrode is prevented as in the conventional case. can do.

It is preferable that a part to be the gate electrode protrudes vertically from a wiring direction of the gate wiring. Thus, the shape of the portion serving as the gate electrode can be freely changed without affecting the wiring width of the gate wiring, so that the shape of the portion serving as the gate electrode is optimized to effectively shield the semiconductor layer. can do.

Further, the source electrode of each TFT is 2
In the case of a TFT having one or more TFTs, the effect of the present invention is particularly large. In the conventional structure, when two or more source electrodes are formed, the semiconductor film is directly exposed to the backlight in a region between the source electrodes. The effect on the off characteristic was particularly large. By applying the present invention,
Since the semiconductor layer can be shielded by the gate electrode in a region between the source electrodes, the off-characteristics of the TFT can be favorably maintained.

The present invention is also an image display application device having the liquid crystal display device according to the present invention. The liquid crystal display device according to the present invention has a T
It is possible to maintain high image quality with little decrease in the off characteristic of the FT. Therefore, an image display application device with high brightness and high image quality can be configured by combining with a high brightness backlight light source.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, members denoted by the same reference numerals as those in FIGS. 3 and 4 represent the same or corresponding members. FIG. 1 is a partially enlarged plan view showing a part of an array substrate in a liquid crystal display device according to the present invention. In the array substrate shown in FIG. 1, the TFT is formed adjacent to the intersection of the gate wiring 4 and the source signal line 5, and has a protrusion (= gate electrode portion 2a) protruding from the gate wiring 5 in a branch shape. A projection (= source electrode portion 5a) protruding from the source wiring 5 in a branch shape is used as a source electrode, and a connection electrode 9 connected to the pixel electrode 10 is used as a drain electrode.

In the present embodiment, the gate electrode portion 2
a vertically protrudes from the gate wiring 2, and a source electrode portion 5 a and a connection electrode 9 are formed orthogonal to the gate electrode portion 2 a. Further, the source electrode portion 5a
Two TFTs are formed for one TFT, and a connection electrode 9 serving as a drain is disposed between these two source electrode portions 5a.

As shown in FIG. 1, the semiconductor layer 4 is formed inside the gate electrode portion 2a in the plane direction except for the intersection with the source electrode portion 5a or the drain electrode 9 and its vicinity. That is, except for a region where the semiconductor layer 4 overlaps the source or drain electrode and a region in the vicinity thereof,
The pattern edge of the semiconductor layer 4 is formed inside the pattern edge of the gate electrode portion 5a. As a result, the semiconductor layer 4 is connected to the source electrode portion 5a or the connection electrode 9
Except for the intersection with and the vicinity thereof, it is hidden inside the gate electrode portion 2a when viewed from the array substrate side.

FIG. 2 is a sectional view of the entire liquid crystal display taken along the line AA 'in FIG. Array substrate 1 made of glass
Gate electrode portion 2a, gate insulating film layer 3, T
Amorphous silicon semiconductor layer 4 for forming FT channel region, etc., passivation film 6, pixel electrode 10
Are sequentially laminated. The passivation film 6 is, for example, an insulating film made of SiNx, SiO ₂ , acrylic resin, polyimide, polyamide, polycarbonate, or a laminated film of these. In this embodiment mode, the TFT is a so-called bottom gate type. That is, the gate electrode 2a
Are formed below the gate oxide film 3, and the source electrode 5 a and the drain electrode 9 are formed above the gate oxide film 3.

As described above, in the conventional liquid crystal display device, since the semiconductor layer 4 is formed to the outside of the gate electrode portion 2a, the backlight light incident from the back surface of the array substrate 1 is emitted from the gate electrode portion 2a. The light was directly incident on the semiconductor layer 4 protruding outside, and unnecessary carriers were induced.

On the other hand, in the liquid crystal display device according to the present invention, as shown in FIG. 2, in the portion opposite to the drain electrode 9, the semiconductor layer 4 is hidden inside the gate electrode portion 2a. No backlight light is incident on the semiconductor layer 4, and an increase in carriers due to light from the back surface on the array substrate side is suppressed as compared with a conventional liquid crystal display device. Therefore, it is possible to suppress a decrease in image performance caused by TFT characteristic deterioration. For example, when a TFT liquid crystal display device using such a TFT configuration was manufactured, a good image display performance with a contrast of 300 or more was obtained even when the incident light luminance was as high as 7000 cd / m ² .

Here, as shown in FIG. 1, at the intersection between the gate electrode portion 2a and the source electrode portion 5a or the connection electrode 9, the semiconductor layer 4 is formed up to the outside of the gate electrode portion 2a. In this portion, the drain region and the source region can be formed in the semiconductor layer 4. Further, since the semiconductor layer 4 is formed not only at the intersection but also in the vicinity thereof to the outside of the gate electrode portion 2a, short-circuit failure between the gate electrode and the source or drain electrode at the edge of the gate electrode portion 2a occurs. Can be prevented.

Except for the intersection with the source or drain electrode and its vicinity, the gate electrode portion 2a is connected to the semiconductor layer 4
In order to position the semiconductor device 4 outside the semiconductor layer 4, the pattern edge of the gate electrode portion may be shifted outward.
May be shifted inward, or a combination of both may be used.

In the present embodiment, as shown in FIG. 1, the pattern edge of the semiconductor layer 4 is formed outside the pattern edge of the gate electrode portion 2a in the region overlapping with the source or drain electrode. The pattern edge of the semiconductor layer 4 and the pattern edge of the gate electrode portion 2a are obliquely intersected with each other just outside and the positions are interchanged. So that it is on the inside.

In this embodiment, two source electrode portions 5a are formed for one TFT, and a connection electrode 9 serving as a drain is disposed between these two source electrode portions 5a. I have. For this reason, the shapes of the gate electrode portion 2a and the semiconductor film 4 are as follows. The gate electrode portion 5a includes two source electrode portions 5
The intersection with a is formed near the drain electrode, and the intersection with the drain electrode is formed near the source wiring, and is formed in a left convex shape as a whole. On the other hand, the intersection of the semiconductor layer 4 with the two source electrode portions 5a is formed closer to the source wiring, and the intersection with the drain electrode 9 is formed closer to the drain electrode. . The gate electrode portion 2a and the semiconductor layer 4 are overlapped with each other in a chain shape. With such a shape, the semiconductor layer 4 can be effectively shielded by the gate wiring 2 even in a configuration having two source electrodes.

Since the liquid crystal display device according to the present invention has the same structure as the conventional liquid crystal display device except for the gate wiring and the pattern shape of the semiconductor layer, a method for manufacturing a conventional general active matrix type liquid crystal display device. Can be manufactured. That is, the gate wiring 2 and the amorphous silicon semiconductor film 4 can be patterned by a general method. For example, a gate film 2 can be formed by depositing a thin film of a metal film for forming the gate wiring 2 by a sputtering film forming method and patterning the metal film by a photolithography process and an etching process.

In this embodiment, the case of a thin film transistor using amorphous silicon for the semiconductor layer has been described as an example, but the present invention is not limited to this. For example, a device using another semiconductor layer such as polycrystalline silicon can also achieve the same operation and effect by adopting a configuration similar to that of the present embodiment.

[0026]

As described above, according to the liquid crystal display device of the present invention, the semiconductor layer is formed so as to be hidden inside the gate electrode except for the intersection with the drain or source electrode and its vicinity. In addition, it is possible to reduce the backlight light directly incident on the semiconductor layer, and to suppress the deterioration of the image performance caused by the deterioration of the off characteristics of the TFT.

[Brief description of the drawings]

FIG. 1 is a partially enlarged plan view showing an array substrate of a liquid crystal display device according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing the liquid crystal display device taken along the line AA ′ in FIG. 1;

FIG. 3 is a partially enlarged plan view showing an array substrate of a conventional liquid crystal display device.

FIG. 4 is a partially enlarged cross-sectional view showing the liquid crystal display device taken along the line BB ′ in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Array substrate 2 Gate wiring 2a Gate electrode part 3 Gate insulating film 4 Amorphous silicon semiconductor layer 5 Source signal line 5a Source electrode part 6 Passivation film 7 Contact hole 9 Drain electrode (= connection electrode) 10 Pixel electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01L 29/78 618C 619B (72) Inventor Ken Shiiba 1006 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H092 JA26 JA28 JA34 JA38 JA42 JB22 JB31 JB57 KA04 KA05 KB24 NA01 NA22 PA13 5C094 AA21 AA25 BA03 BA43 CA19 DA13 EA03 EA04 EA07 EB02 FA02 FB14 5F110 AA06 AA30 BB01 NN0123 GG02 NN0123 NN44 NN72

Claims (4)

[Claims] A plurality of pixel electrodes arranged in a matrix on an insulating transparent substrate, a source line formed between columns of the pixel electrodes, and a gate line formed between rows of the pixel electrodes. A semiconductor layer formed in a one-to-one island shape on the pixel electrode, and a connection electrode connecting the semiconductor layer and the pixel electrode, wherein the semiconductor layer uses a part of the source wiring as a source electrode. A liquid crystal display device comprising a thin film transistor using a part of the gate wiring as a gate electrode and the connection electrode as a drain electrode, wherein the semiconductor layer has an intersection with the source wiring or the connection electrode and a vicinity thereof; A liquid crystal display device, wherein the liquid crystal display device is located inside the gate wiring in a plane direction except for the gate wiring. 2. The liquid crystal display device according to claim 1, wherein a portion serving as the gate electrode protrudes vertically from a wiring direction of the gate wiring. 3. The liquid crystal display device according to claim 1, wherein each of the semiconductor layers has two or more portions serving as the source electrodes. 4. An image display application device having the liquid crystal display device according to claim 1.